//tests/rpm:test_golden_debuginfo_rpm_contents fails to build on some machines

`bazelisk test --sandbox_debug //tests/rpm:test_golden_debuginfo_rpm_contents`

fails with
```
...
# pkg_rpm emits two outputs
RPMS=(bazel-out/k8-fastbuild/bin/tests/rpm/test_debuginfo_rpm-1-0..rpm)
echo "===== main RPM =====" > bazel-out/k8-fastbuild/bin/tests/rpm/test_debuginfo_rpm_contents.txt
rpm -qpi --list ${RPMS[0]} | grep -v '\''Build Date'\'' | grep -v '\''Build Host'\'' | grep -v '\''Relocations'\'' | grep -v '\''Architecture'\'' | grep -v '\''Size'\'' | grep -v '\''.build-id'\'' >> bazel-out/k8-fastbuild/bin/tests/rpm/test_debuginfo_rpm_contents.txt
echo "===== sub RPM ======" >> bazel-out/k8-fastbuild/bin/tests/rpm/test_debuginfo_rpm_contents.txt
rpm -qpi --list ${RPMS[1]} | grep -v '\''Build Date'\'' | grep -v '\''Build Host'\'' | grep -v '\''Relocations'\'' | grep -v '\''Architecture'\'' | grep -v '\''Size'\'' | grep -v '\''.build-id'\'' >> bazel-out/k8-fastbuild/bin/tests/rpm/test_debuginfo_rpm_contents.txt
')
/bin/bash: line 7: RPMS[1]: unbound variable
```

We are only getting 1 declared output of the rpm, and not the debug one.
Perhaps this is an RPM version difference?

cc:@kellyma2